Filter cartridge

ABSTRACT

An improved precoat filter cartridge and a method of applying the precoat medium thereto. The filter cartridge comprises: a vertically extending tubular core element having apertures therein; a filter screen positioned about said core element to receive precoat particles; and a cover member closing off the upper portion of said core element defining a chamber formed by the sides thereof to accumulate gas trapped within said cartridge. A vent hole is provided in said cover member to permit the trapped gas to be vented therethrough.

United States Patent Ryan Dec. 18, 1973 FILTER CARTRIDGE 3.178.0214/1965 Bray 210/75 x 1,l37,4 41915 ..210497X [75] Inventor: Leo F. Ryan,Somerville, NJ. 80 Gwyn" [73] Assignee: Ecodyne Corporation, Chicago,111. Primary ExaminerSamih N. Zaharna' Assistant Examiner-Robert H.Spitzer [22] Flled' 1972 Attorney-Char1es M. Kaplan et a1. [21] Appl.No.: 237,568

' Related US. Application Data [57] ABSTRACT [62] Division of Ser. No.87,661, Nov. 9, 1970, Pat. No. An improved Precoat filter Cartridge anda method of References Cited UNITED STATES PATENTS 10/1968 Bush et a1.210/297 X applying the precoat medium thereto. The filter cartridgecomprises: a vertically extending tubular core element having aperturestherein; a filter screen positioned about said core element to receiveprecoat par ticles; and a cover member closing off the upper portion ofsaid core element defining a chamber formed by the sides thereof toaccumulate gas trapped within said cartridge. A vent hole is provided insaid cover member to permit the trapped gas to be vented therethrough.

3 Claims, 2 Drawing Figures I d z/ z a;

I I I z i 0 /3 O $55 M o i H z I FILTER CARTRIDGE This is a division, ofapplication Ser. No. 87,661, filed Nov. 9, 1970, now US. Pat. No.3,680,700.

BACKGROUND OF THE INVENTION The present invention relates to an improvedfiltration system and more particularly to an improved precoat filtercartridge for applying the precoat medium thereto.

Liquids may be very effectively purified by passing them through afilter screen which has been precoated with a layer of ion exchangeresin particles in the size range of 60 to 400 mesh, hereinafterreferred to as precoat medium. This method is disclosed in U.S. Pat. No.3,250,703, issued May 10, 1966, and assigned to the assignee of thisinvention.

In the typical system of this type a plurality of filter cartridges arespaced within a filter tank. Precoat filter cartridges of this typegenerally include a core element of suitable corrosion resistantmaterial having openings therethrough. The body portion is covered witha layer of coarse screen which, in turn, is wrapped with a layer of finemesh screen. In order to precoat the filter cartridges a water slurry ofprecoat medium is passed through the filter tank. A precoat layer ofprecoat medium is thereby deposited upon the upstream sides of thefilter cartridges. A precoat layer of uniform distribution throughoutthe entire length of the filter cartridges is desirable for maximumutilization of the system.

It has been discovered that during filling of the filter tank with watera certain amount of air or other gasses are trapped in the upper portionof each filter cartridge due to capillary resistance. This has at leasttwo deleterious effects on the filtration system. Firstly, the gasprevents the flow of slurry through those areas of the cartridges inwhich it is located and thereby prevents precoating; and secondly,during the filtering cycle of the system, gas is periodically releasedoutwardly through the filter cartridges and disrupts the precoatthereon.

This problem of accumulated gas within the precoat cartridges isespecially prevalent with precoat media having low pressure dropcharacteristics such as powdered ion exchange resins. The only attemptsto solve this problem in the past have been attempts to minimize the gasin the incoming water entering the system. This has not beensatisfactory because of the obvious difficulty of preventing gas fromentering the system.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a precoat filter cartridge that reduces the accumulation of airor other-gasses within the cartridge and thereby permits a more uniformprecoat layer to be deposited upon the cartridge.

Another object of the invention is to provide a precoat filter cartridgethat includes a vent hole to permit the removal of air or other gassesaccumulated therein.

A further object is to provide a precoat filter cartridge that includesa dome cover surrounding the upper portion of the filter cartridgewherein gas may be accumulated so as not to disturb the precoat layer.

Astill further object is to provide a precoat filter cartridge that willprovide a uniform precoat, especially towards the upper portion of thecartridge.

The present invention provides a precoat filter cartridge having a domeshaped cover around the upper portion of the cartridge. The coverincludes a vent hole communicating with the internal portion of thefilter cartridge. The invention further provides a method of precoatingthe cartridges which comprises: a) filling the filter tank with water ata relatively low pressure; b) increasing the pressure of the waterwithin the tank; and c) cycling a precoat slurry through the tank. Byincreasing the pressure of the water within the tank prior to precoatingthe accumulated gas is compressed and vented through the hole in thedome shaped cover.

DESCRIPTION OF THE DRAWING Other objects and advantages of the inventionwill hereinafter become more fully apparent from the followingdescription of the annexed drawing, which illustrates a preferredembodiment, and wherein:

FIG. 1 is a schematic representation of a filtering system of the typewhich utilizes the filter cartridges of the present invention; and

FIG. 2 is an enlarged partial cross sectional view of one of the filtercartridges illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. I, there isillustrated schematically a filter system, indicated generally by thereference numeral 10, for removing dissolved and undissolved impuritiesfrom water in accordance with the present invention. Although thepresent invention will be discussed in detail with respect to thepurification of water, the present invention has application to thepurification of gasses and other liquids.

The filtration system 10 comprises a filter tank 12 having an inletconduit 14 and an outlet conduit 16. Filter tank 12 is generally acylindrical vessel made of steel, or the like having outwardly convextop and bottom portions 18 and 20, respectively. Tank 12 is partitionedinto an influent zone 22 and an effluent zone 24 by a downwardly convextube sheet plate 26 suitably secured to the interior of the tank bywelding or the like.

Inlet conduit 14 enters tank 12 through the bottom end 20 and passesupwardly through effluent zone 24 and plate 26 to communicate withinfluent zone 22. Conduit 14 is attatched to plate 26 by welding or thelike, so as to preclude fluid leakage from influent zone 22 to effluentzone 24. Fluid entering influent zone 24 through inlet conduit 14 isdistributed radially outwardly by distribution plate 28.

Mounted within the influent zone 22 are a plurality of filter cartridges30 through which the influent stream must pass before entering effluentzone 24 and being discharged from filter tank 12 through outlet conduit16. Eachfilter cartridge 30 is held in place in influent zone 22 offilter tank 12 by a holding assembly, indicated generally by referencenumeral 32. The selection of a suitable holding assembly would, ofcourse, be within the ordinary skill of one in the art. Holdingassembly'32 is adopted to releasably hold filter cartridges 30 in placeupon filter seat means 34 which are attached to plate 26. Filtercartridges 30 are placed into and removed from filter tank 12 through amanhole opening 36 in filter tank 12. Manhole opening 36 has acovermeans 38 which may be removed or opened, as

desired, to provide access to the interior of filter tank 12.

Filter seat means 34 comprises a small pipe made of steel or the likewhich extends through a hole in plate 26 and is attached to plate 26 bywelding or other suitable means. Filter seat means 34 is substantiallyparallel to the longitudinal axis of filter tank 12 and connectsinfluent zone 22 with effluent zone 24. Filter seat means 34 provides abase for the filter cartridge 30, which is held in position on means 34.

The filter tank is also provided with a vent 39. Vent 39 may be of anysuitable construction, the selection of appropriate vent means beingdependent generally upon the specific use of the filter system 10.

A water slurry of the particular precoat medium (e.g. finely divided ionexchange resin particles in the size range of about 60 to 400 mesh) isstored in a precoat tank 40. A slurry line 41, controlled by a slurryvalve 42, connects precoat tank 40 with a slurry pump 43. A transferline 44 connects pump 43 with inlet conduit 14 of filter tank 12. Atransfer valve 45 adjacent the pump 43 and in transfer line 44 controlsthe passage of slurry from pump 43.

The water to be treated enters filter system through feed line 46 havingan intake control valve 47. Feed line 46 is connected to transfer line44 between control transfer valve 45 and inlet conduit 14.

Outlet line 16 is connected to a service line 48 and a precoat returnline 49 at a T-juncture indicated by reference numeral 50. Service line48 is connected to service units not shown, such as a steam generatorand the like, and has a service valve 51. The precoat return line 49 isconnected to the precoat tank 40 and has a return valve 52 to controlthe flow of slurry back to precoat tank 40. Backwash line 57 isconnected to outlet line 16 and has a valve 58 to control the flow ofbackwash water into tank 12. A bridge line 53 with a bridge valve 54interconnects the precoat return line 49 and the slurry line 41. Filtersystem 10 is equipped with a vent valve 55 and drain valve 56.

Referring to FIG. 2, each filter cartridge 30 includes as inner coreelement 60 of suitable corrosion-resistant material such as aluminum orstainless steel having holes 62 therein. Core element 60 is covered witha layer of coarse drain mesh 65 which, in turn is wrapped with a layerof fine mesh screen 68. Filter cartridge 30 includes a dome shaped covermember 70 closing off the upper portion of core element 60 so as todefine a chamber 71 between the side walls thereof. Vent hole 72 passesthrough the upper portion of cover member 70 so as to permit fluidcommunication between chamber 71 and influent zone 22. Core element 60and screens 65 and 68 extend upward beyond vent hole 72 so as to preventprecoat material from entering chamber 71 through vent hole 72.

In preparing the filter system 10 for operation the initial step is toprecoat the filter cartridges 30. To these ends, the filter tank 12 isfilled with a low impurity water, such as demineralized water, at arelatively low pressure, i.e. approximately 8 p.s.i.. Tank 12 is filledby passing the demineralized water through backwash line 57 and intotank 12 via outlet line 16. During this filling step all the valves areclosed, except valve 58 and vent valve 55. Due to capillary resistanceair or other gasses may be trapped in the upper portions of cartridges30 and in chambers 71. The pressure of the water in tank 12 is causedbythe back pressure resulting from controlling valve 55. Upon fillingtank 12 with demineralized water at a relatively low pressure all valvesare closed.

A slurry of precoat medium and demineralized water is prepared inprecoat tank 40. The precoating step is initiated by opening slurryvalve 42, transfer valve 45 and return valve 52 and starting purnp 43,thereby drawing the precoat slurry from precoat tank 40 through transferline 44 into filter tank 12 via inlet conduit 14. The pressure of theincoming slurry forces the demineralized water in filter tank 12 throughscreens 68 and 65 and core elements into filter cartridges 30 and out ofthe filter tank 12 via conduit 16. This demineralized water enters theprecoat tank 40 through the return line 49. Return valve 52 iscontrolled so as to create a back pressure in tank 12 which increasesthe pressure of the water in tank 12. By increasing the pressure of thewater in tank 12 the gas trapped in the upper portions of cartridges 30are compressed upward into chamber 71 and partially forced out throughvent hole 72. Tests have shown that by doubling the pressure in tank 12from approximately 8 p.s.i. to 16 p.s.i. all the trapped gas in thefilter cartridges 30 is forced upward into chamber 71 thereby permittinga uniform precoat over the entire length of the cartridges below covermember 70. This increased pressure is retained in the system during theprecoat cycle and the service cycle so as to continue to confine thegas.

As the cycling continues the precoat slurry is brought into contact withthe upstream surfaces of the filter screens 68 of filter cartridges 30.The particles of the precoat medium are separated from the slurry anddeposited as a precoat layer upon the upstream surfaces of the screens68. The slurry is circulated through the filter system in this manneruntil sufficient depth of the precoat is deposited upon the upstreamsurface of filter screens 68. The precoating step is terminated byclosing slurry valve 42 and return valve 52 and opening bridge valve 54.Pump 43 is kept running until the recycle stream is clear. The filtersystem is now ready to be used to treat the service water.

The service cycle is begun by closing bridge valve 54 and transfer valve45 and opening service valve 51 and feed valve 47. This step ispreferably timed to maintain sufilcient pressure in the system to assureretention of the precoat layer on filter screens 68. In this manner,untreated water enters the filter system through feed line 46, passesthrough transfer line 44 and passes through inlet conduit 14 to influentzone 22. The pressure of the incoming untreated water forces it throughthe precoat layers, filter screens 68 and and core elements 60 intofilter cartridges 30 and out through outlet conduit 16. As the untreatedwater passes through the precoat layers, impurities are removed from thewater. The treated water flows through outlet conduit 16 to service line48.

Eventually the precoat material will become exhausted and must bereplaced. At this time the filtering step is stopped by closing intakevalve 47 and service valve 51. Vent valve 55 and drain valve 56 areopened to drain filter tank 12. The filter cartridges 30 are washed byan internal washing system, not described or shown. Another charge ofprecoat material is then placed in the precoat tank 40 and the processof precoating and filtering describedin detail hereinbefore is repeated.

It has been shown that by increasing pressure and venting the top of afilter cartridge so as to compress and expel gas trapped therein; thepresent invention prevents such gas from blocking flow of a slurry thatis depositing a precoat on the cartridge.

Though the apparatus of the present invention has been discussedprimarily in connection with a precoat material of finely divided ionexchange resin particles, it may likewise be used where the precoatmaterial is of another material such as diatomaceous earth, or any otherprecoat materials, as will be understood by those skilled in the art.

Obviously, many modifications and variations of the present invention ashereinafter set forth will occur to those skilled in the art, and it isintended to cover in the appended claims all such modifications andvariations as fall within the true spirit and scope of the invention.

What is claimed is: j

1. In a liquid filtering apparatus including a filter tank, a plateseparating said tank into an upper influent compartment and a lowerfiltrate compartment, a plurality of annular filter cartridgesvertically mounted in said influent compartment, and precoat meansincluding means for distributing precoat particles on said filtercartridges; each of said filter cartridges comprising:

a. a vertically extending tubular core element having apertures therin;

b. a filter screen positioned about said core element to receive saidprecoat particles; and

0. cover member means closing off the upper portion of said core elementdefining a chamber having substantially imperforate walls formed by thesides thereof in direct and free communication with said filtercartridge interior for accumulating gas trapped within said filtercartridge upon increase of the liquid pressure within said tank in anarea remote from the filtering area of said filter cartridge so as topermit said precoat to deposit on said filtering area in a uniformlayer.

2. The precoat filter cartridge as defined in claim 1 wherein said covermemeber means includes a vent hole passing therethrough so as to permitsaid trapped gas to be vented therethrough.

3. The precoat filter cartridge as defined in claim 2 wherein saidfilter screen covers said vent hole.

1. In a liquid filtering apparatus including a filter tank, a plateseparating said tank into an upper influent compartment and a lowerfiltrate compartment, a plurality of annular filter cartridgesvertically mounted in said influent compartment, and precoat meansincluding means for distributing precoat particles on said filtercartridges; each of said filter cartridges comprising: a. a verticallyextending tubular core element having apertuRes therin; b. a filterscreen positioned about said core element to receive said precoatparticles; and c. cover member means closing off the upper portion ofsaid core element defining a chamber having substantially imperforatewalls formed by the sides thereof in direct and free communication withsaid filter cartridge interior for accumulating gas trapped within saidfilter cartridge upon increase of the liquid pressure within said tankin an area remote from the filtering area of said filter cartridge so asto permit said precoat to deposit on said filtering area in a uniformlayer.
 2. The precoat filter cartridge as defined in claim 1 whereinsaid cover memeber means includes a vent hole passing therethrough so asto permit said trapped gas to be vented therethrough.
 3. The precoatfilter cartridge as defined in claim 2 wherein said filter screen coverssaid vent hole.